The main objective of the proposed research is to identify chemically the presumptive primary afferent sensory transmitter(s) of the lateral line organ of Xenopus laevis (the African clawed frog) and of the cochlea of the guinea pig, and to characterize the biochemical systems associated with the presumptive transmitter(s). Analytical methods include: (1) micro fluorescence amino-acid analysis with orthophthaldialdehyde/2-mercaptoethanol, for detection of primary amines, (2) anion-exchange and high-performance-liquid cation-exchange chromatography, for detection of mixtures and radioactively labeled small molecules, (3) disc-gel electrophoresis and column chromatography, for purification of lateral-line neuromast proteins, and (4) a bioassay using the Xenopus lateral-line, for detecting neurotransmitter-like activity. Preparative methods include: (1) dissection of stimulated or non-stimulated lyophilized Xenopus neuromasts, prior to determination of their small-molecule content and enzymatic activity, (2) a surgical approach to the guinea-pig cochlea and temporal bone for collection of perilymph, cerebrospinal fluid (CSF), and CSF-free perilymph in the presence and absence of noise, before determining the small-molecule content of these fluids, and (3) the isolation, for chemical analysis, of synaptic vesicles from neuromasts of Xenopus. Using these methods, we plan to establish the identity, and presence in the lateral-line neuromast, of the presumptive Xenopus lateral-line transmitter(s), its (their) associated synthetic and degrading enzymes, and its (their) biological activity. We aslo plan to establish the identity, stimulated release into perilymph, and biological activity (or inactivity) in the lateral-line bioassay, of the presumptive guinea-pig cochlear transmitter(s). We further plan to identify chemically nontransmitter materials that are released into perilymph during exposure of the guinea pig to noise at high levels, in order to distinguish such materials from presumptive transmitters released at lower levels, and to characterize further the graded response of the auditory system to noise.